From the site:
"Simplify. Organize. (And relax.) Organizing your schedule shouldn't be a burden. That's why we've created Google Calendar – our free online shareable calendar service. With Google Calendar, it's easy to keep track of all your life's important events – birthdays, reunions, little league games, doctor's appointments – all in one place.
Using Google Calendar, you can add events and invitations effortlessly, share with friends and family (or keep things to yourself), and search across the web for events you might enjoy. It's organizing made easy."